Each day people are more brazen and rude with their cellphones. My husband bought a device that can block the signals of cellphone users who annoy him, although he knows such gizmos are illegal. Isn’t his vigilante behavior worse than that of the rudest cell user? — Name Withheld, Connecticut

Your husband may not stifle someone’s behavior merely because he deems it annoying. So capricious a standard would mean constant peril for people who talk baby-talk to their excessively small dogs. Living among other people requires us to tolerate conduct we find vexing.

Or so my head tells me. But my heart says, Your husband is a hero, an acoustic Robin Hood who robs from the rude and gives blessed silence to the poor in spirit.

I propose these guidelines: If someone is yammering into a cellphone on the pavement and you don’t like it, walk away. It is open public space, and opinions vary about its use. Some people place a lower value on quiet than on prattling about what they saw on TV last night. (An immutable law of nature: The louder the phone voice, the duller the conversation.)

But if someone is using a cellphone in a closed space — on a commuter train, in a restaurant — from which you cannot escape, let the jamming begin. We properly limit our freedom when we harm others. It is the cellphoner’s jabbering that prevents you from reading your book or thinking your thoughts, not the other way around.

Those who control shared closed spaces — a theater, a physician’s waiting room — should jam and disclose. Post a sign that says “No Cellphone Service” so people know what they’re getting into. Anyone anticipating an urgent call can ask to use the land line. For decades, doctors on call did just that, and we all survived. Sadly, this solution — ethical, courteous and humane — is frowned on by the F.C.C., but tell your husband I’ll visit him every week in jail.